Electric glow-lamp.



No. 685,727. Patented Oct. 29, IQOI. W. NERNST.

ELECTRIC GLOW LAMP.

(Application filed Apr. 10, 1901.)

(No Model.)

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UNITED STATES PATENT @FEICE.

WALTIIER NERNST, 'oF-co'rTINcEN, GERMANY, ASSIGNORYTO GEORGEWESTINGHOUSE, E PITTSBURG, PENNSYLVANIA.

ELECTRIC GLOW-Y-LAMP'.

s'PEcIEicATroN forming part of Letters Patent No. 685,727, dated October29, 1901..

Original application filed April 28, 1898, Serial No. 679,081. Dividedand application filed May 29, 1899, Serial No. 718,624; Again dividedand this application filed April 10,1901. Serial No. 55,221-l (Nomodel.)

To (ZZZ whom it may concern.-

Be it known that I, WALTHER NERNST, a subject of the Emperor of Germany,and a resident of Gottingen, Germany, have invented certain new anduseful Improvements in Electric Glow-Lamps, (division of an applicationfiled by me April 28, 1898, Serial No. 679,081,) of which the followingis a specification.

My invention relates in a general way to the class of devices known asincandescent electric lamps and a method of lighting; but it diifersfundamentally from the incandescent lamps and methods heretofore usedand involves certain peculiar features and characteristics which justifyits classification as a distinct and novel species.

Heretofore all practical incandescent electric lamps have comprised afilament of conducting material, usually, if not always, of carbon,contained within an inclosing chamher from which the air is exhausted.The fact that the filaments heretofore employed will oxidize when heatedin the open air has necessitated inclosing them in vacuum-chambers.

Various refractory materials comprising certain oxids, sulfids,silicates, and other saltrefractory materials were to be used inconnection with electric lighting at ordinary voltages, it hasheretofore been considered necessary to either maintain them in anincandescent st-ate by placing them in proximity to conductors heated byelectric currents on to coat them or add to them 'or in some way combinewith them'some good conducting material, such as a metal or carbon,whichshould afford a conducting-path for the current. For example, it hasbeen proposed to impregnate or coat conductors-such, for instance, asplatinum, iridium, 0r carbonwith a refracmelts or disintegrates orcauses the refractorymaterial to crack off or disintegrate.

I have discovered that certain refractory salt-like combinations,particularly oxide usually classed as the rare earths, which are atordinary temperatures non-conductors of electricity, as that term isusually employed, will when raised to the high temperature ofincandescence become sufficiently good conductors to permit the passageof an electric current under moderate differences of potential and maybe maintained sufficiently heated to retain their thus-acquiredconducting qualities by the passage of the electric currenttherethrough. These materials when so traversed by electric currents notonly emit more light under the influence of a given amount of electricalenergy than the ordinary incandescent lamp, but they also resist Idecomposition and disintegration even in the open air, and therefore alamp constructed in accordance with my invention does not require avacuum-chamber, though a vacuumchamber may be used in certain cases, ifdesired.

The general character-i. ing portion of my lamp are so widely differentfrom those of the ordinary incandescent electric lamp that to term it afilament would be not only inappropriate, but to a certain extentmisleading. The light is emitted therefrom without combustion ormaterial disintegration even when exposed to the air, and beingtranslucent it emits light from its interior and from its surface, and Ihave given the name glower to the light-giving portion and glow-lamp tothe lamp itself as being properly applicable.

The materials which I have discovered to possess the qualities abovereferred to may be classed under the general term of dry stics of thelight-givelectrolytes or dry conductors of the second class. By theexpression conductors of the second class I refer to those which when ina conducting condition conduct cur rent by electrolytic action.

Prominent among the materials with which I have obtained excellentresults may be mentioned oxid of magnesium, or magnesia, and oxid ofzirconium, or zirconia; also, the oxids of yttrium, cerium, thorium, andthe like. These materials when in a dry state and at normal temperaturesare practically insulators or non-conductors; but when glowers made fromthem are heated to a state of incandescence they acquire conductingqualities to such an extent that electricity may be caused to passthrough them at ordinary low pressures in sufficient quantities to keepthem in the state of incandescence even after the means employed forimparting the original starting-heat is withdrawn. Instead of usingthese materials individually or alone for forming the glower two or moreof them may be mixed or combined in varying proportions withadvantageous results. Glowers made from a proper mixture of certain ofthe materials will pass into the conducting state at a lower initial orstarting temperature than will a glower madev from one of the materialsalone and will maintain, under the passage of the electric current, aluminous condition without deterioration better and for a longer timethan will any single one of such materials. It is not, therefore, themere mixture of such materials that I prescribe, but the utilization ofsuch mixtures on account of their superior properties when brought toand maintained in a luminous condition. These materials even when intheir best operating conducting condition have a specific resistance sogreat with reference to that of carbon that a glower to be used with agiven voltage may be much shorter and thicker than the carbon filamentof an ordinary incandescent lamp. For instance, a practical glower of,say, one-fiftieth'of an inch in diameter and one-half an inch in lengthmay be made which when heated to a low incandescence will become asufficiently good c011- ductor to be traversed nnder'a one-hundredvoltdifference of potential by a sufficient current to bring it to andmaintain it at a state of high incandescence. A current of, say,four-tenths of an ampere, or thereabout, will accomplish this result. Asthe material has sufficient strength to enable it to be used in muchlonger lengths than that above referred to, it is possible to constructlamps adapted to be operated at'very much higher voltages than ispracticable with lamps using carbon filaments, a feature which may beutilized to obtain economy of transmission. This feature,

in connection with the high efficiency of the lamp, renders it possibleto secure either a given illumination with a much higher transmissioneiliciency than at present obtained or a higher illumination withthe'present transmission efliciency, or both the illuminating andtransmission efficiencies may be materially increased.

There are numerous diiferent proportions in which the differentrefractory materials adapted to the purposes of my invention may beused, and there is a very wide range for the selection of the differentmaterials to be mixed together, and therefore I will attempt only, andit will only be necessary, to specify one or two examples. Veryexcellent results have been obtained from a mixture of approximatelyseventy per cent. of zirconia and thirty percent. of yttria, (oxid ofyttrium.) Another mixture which I have used with good advantage consistsof approximately ten per cent. of zirconia, seventy percent. of thoria,and twenty per cent. of yttria. I have also obtained excellent glowersfrom a mixture of about seventy per cent. of thoria and thirty per cent.of yttria. Another mixture consists of 0.5 per cent. of ceria, eightyper cent. of thoria, with 19.5 per cent of yttria. These percentages maybe widely varied, and, generally speaking, the oxide of the rare earthsare well adapted for mixture in widelyvarying proportions.

The process of preparing the glowers from which I have heretoforeobtained the best results when two or more of theoxids are to be usedtogether consists in thoroughly pulverizing and mixing the materialstogether into very intimate relations, then mixing therewith a binder ofclear-starch paste, making a plastic mass which should be thoroughlyworked. The water used in making the paste should be clear andpreferably distilled to avoid the presence of lime, which is morevolatile than the oxids of the rare earths, and therefore undesirable.The plastic mass may then be inserted in a press adapted to force themixture through a small hole of the requisite diameter, dependent uponthe ultimate diameter desired for the glower, and as the material leavesthe press it may be hung over aglass rod or laid upon a suitablesupportingsurface and allowed to dry. The material acquires sufficientstrength when dried to be conveniently handled, and it is then heated toa very high temperature in any suitable manner-for instance, in anoxyhydrogen flame. It is desirable that as great a specific gravity aspossible may be given to the material-that is to say, the smallestdiameter for a given mass of a given length. Care should be taken thatevery part of the glower is brought to a high incandescence. Usually itis advantageous to heat the material gradually, so as to drive off themoisture and the binding material slowly, and thus lessen the liabilityof the surface becoming cracked. For example, it may be passed through apreliminary heat in a porcelain kiln. The eventual heating, however,should be carried to an extremely high temperature. \Vhen the materialhas been thus prepared, a proper length, dependent upon the voltage andcurrent with which it IIO is to be used, is mounted between two suitablecond noting-wires. The ends may advantageously be fastened mechanicallyin any suitable wayas, for-instance, by inserting them into suitablesockets made by forming into spirals the-conducting-wires, which may beof platinum or other good conducting materials which melt only at a veryhigh temperature. The junctions of the glower with the respective wires'are then built up by placing thereon in a liquid or paste-like conditionsmall quantities of acementing material and heating and drying the samein a gas-flame or otherwise. This process is repeated until a firm unionis obtained between the respective ends of the glower and the wires. Itis advantageous also to make the points of juncture with the wires oflarger diameter than the main portion of the glower, for then the pointsof contact with the wire will not during the operation of the lamp be ashot as the remainder of the glower, and therefore the wires themselvesare less liable to burn olf. The paste or cement with which it isdesirable to build up the ends may be of the same material as that usedfor forming the glower itself. I have obtained excellent results bypulverizing portions of glowers which have been previously prepared andheated to high temperatures and mixing the same with water, and, ifdesired, starch-paste may be added. Any suitable means for sup portingthe conducting-wires and securing electrical connections therewith maybe employed.

For the purpose of obtaining the preliminary or starting heating of theglower various different means maybe employed. Usually it is desirablethat the heat should be applied only during the starting process andthenwithdrawn, although in some cases it maybe desired to continue theextraneous heat while the lamp itself is in operation. A very convenientstarting-heater consists of a coil of platinum wire or other conductingmaterial which may be heated to a high temperature in the open air bythe passage of electric currents without being melted. This wire iscoiled or otherwise arranged in such proximity to the glower that whenheated by the passage of an electric current it will raise the glower toa sufficiently high temperature.

to cause it to acquire the necessary conducting capacity to permitsufficient current to flow through it under the influence of thedifference of potential of the circuit upon which it is to be used tocarry it to a state of high incandescence and maintain it there. Whenthe lamp has once been started, the circuit through the heater may beinterrupted manually or automatically, and, if it is desired, the heatermay also be withdrawn from the immediate vicinity of the glower. In-

stead of imparting the starting-heat by the agency of electric currentsother extraneous sources of heat may be employedas, for instance, agas-flame or the flame of a lamp, or even a match in some instances.

The temperature to which the glower must be brought in order to havesufficient conductivity to allow enough current to flow through it tomaintain itself in that conductive condition varies somewhatlwithdifferent materials and proportions. Some of the mixtures will produce aglower which when heated to a conductive temperature will fall inresistance as rapidly under the influence of a constant difierence ofpotential as to permit a current to flow which would be destructive tothe glower. With such glowers means should be employed for counteractingthis effect and cause the glower to receive and consume only apredetermined amount of current,and therefore remain at a predeterminedsafe temperature. A convenient means for accomplishing this result withsuch glowers consists in introducing in series with the glower acorrectly proportioned resistance, preferably having a high positivetemperature coefficient, and therefore offering an increasing oppositionto the flow of the current with increments of current. Resistancescomposed of materials having little or no positive temperaturecorrections may, however, be usedin cer tain cases. In constant-potential alternating-' current circuits reactive coils may be used inlieu of such resistance as above referred to. The expenditure of energyin such compensatingdevices when required may be very low, as theireffective resistance may be in some cases as low as two per cent. oreven less of the resistance oifered by the glower when in operation ifthe lamps are used upon circuits having little or no variation indifference of potential-as, for instance, storagebattery circuits. Whenused upon circuits subject to wider-variations, it may be'desirable thatthis resistance should consume as much as five per cent. or even more.alternating-current circuits where reactive coils are used less thanthis will usually suflice.

The present applicatiomwhich is a division of my application, Serial No.679,081, dated April 28, 1898, relates more particularly to that featureof the original application which is concerned with the arrangement ofthe heating-body in an independent circuit with respect to the glowerand also to the use of a transparent material as the support for theheater.

Upon

' The present invention is illustrated in the 'pleted to thebinding-posts c c of the lamp. The light-giving portion or glower A ofthe lamp is made in accordance with the description hereinbefore given.It is carried by two conductors a a of any suitable character, and theseare connected with the terminals '0 c of the lamp. A bridge-piece a maybe employed for holding the conductors a. a in their proper relativeposition. A heating or starting conductor B is shown in Fig. 1 ascarried upon a glass or other transparent support II, and it incloses toa greater or less extent the glower A. Suitable supportingclips ff areprovided for receiving the ends of the supports a (t so that a glowermay be readily replaced. The heater-support II is here mounted, throughthe medium of a standard 0 and bracket 0 so that both the support II andits heating-conductor B remain stationary. On the other hand, the glowerA and the parts connected therewith are mounted upon a movable bracketK, connected with the core 7c of a solenoid K, forming part of theglower-circuit. The core 7.; is supported by a spring t, connected witha horizontal extension of the standard 0. A downward movement of thecore 71: within its solenoid will move the glower out from the inclosingsupport II. A rod *1", passing through an openingoflservestoguidetheparts throughout their motion. It will be understood that insome cases it may not be desired to separate the heater and the glowerfrom each other, in which case light from the glower will be transmittedthrough the transparent heater-support. In this instanceI have shown theheater as being supplied from a separate source G of electricity insteadof being in a branch circuit from the source G. The source G and thesource G may either or both of them be sources of alternating orcontinuous current, as desired. In the heater-circuit I place a switch.9, by means of which the circuit may be opened or closed. An automaticcircuit-interrupting device may be placed in the circuit of the heater,if desired. WVhen the switches D and s are closed, the current passesthrough the heater B, raising the glower A to such a temperature as willrender it sufficiently conductive to be traversed by the current fromthe generator G. The solenoid K will then be energized, drawing down thecore against the force of the springt and removing the glower A fromwithin the inclosing support H. The circuit through the heater may thenbe interrupted by means of the switch 5, if desired. The interruption ofthe circuit through the glower automatically restores the parts to thepositions shown in Fig. 1.

Ghana"? By requirement of the Patent Office this application is dividedout of my application, Serial No. 718,624, which was filed May 20, 1899,as a division, of an earlier application, Serial No. 679,081, filedApril 28, 1898.

I claim as my invention 1. In an electric-lighting system, a source ofelectric current, a glower which is nonconductive when cold and requiresto be heated to be rendered conductive, in circuit with the said source,and an electric heater in an independent circuit and located in proimity to the said glower.

2. In an electric-lighting system, a source of electric current, aglower which is nonconductive when cold and requires to be heated to berendered conductive, in circuit with the said source, an electric heaterin an independent circuit and located in proximity to the glower, and aswitch in the heatercircuit for controlling the operation of the heater.

S. In an electric-lighting system, a source of electric current, aglower which is nonconductive when cold and requires to be heated to berendered conductive, in circuit with the said source, an electric heaterin an independent circuit and located in proximity to the said glower,and switches in the glower and heater circuits for controlling theiroperation.

4. In electric lamps, the combination with an incandescent body made ofa material that is a non-conductor whencold and becomes a conductor whenheated to a high temperature, of a resistance-conductor, a support offireproof non conducting and transparent material surrounding the saidincandescent body, and means for heating said resistance-conductor bythe passage of electric currents, substantially as and for the purposedescribed.

5. Inelectricalincandescentlamps,thecombination with an incandescentbody made of a material that isa non-conductor when cold and becomes aconductor when heated to a high temperature, of a wire resistancecombined with a sleeve of fireproof non-conducting and transparentmaterial such as glass surrounding the said incandescent body, and meansfor electrically heating said wire resistance, substantially as and forthe purpose described.

Signed by me at Berlin this 27th of March, 1901.

WALTHER NERNST.

Witnesses:

WOLDEMAR IIAUPT, HENRY I'IASPER.

